This Implant (1) includes, in a known manner, two pieces (2, 3) that are telescopically mobile relative to one another and elements (4) for positioning one piece (3) in a particular position relative to the other piece (2), the two pieces (2, 3) being made from a polymer material. At least one of the two pieces (2, 3) has a plurality of micro-cavities (15, 20, 32) over at least one wide portion of its peripheral wall (5)； and the implant includes internal communications (16, 21, 33) in its wall(s) (5, 7, 31) including the micro-cavities (15, 20, 32), connecting all or some of the micro-cavities to one another.
